1. Field of the Invention
The present invention relates to a radio-frequency (RF) system, and more particularly, to an RF system capable of providing additional transmitting and receiving capabilities without substantially enlarging disposal area.
2. Description of the Prior Art
An array antenna is an antenna system composed of a plurality of identical antennas arranged in accordance with a specific rule. Through proper arrangement of antenna element of the array antenna, a specific radiation pattern is achieved to concentrate a main beam at a specific direction to transmit signals. For example, for vehicle radar systems, the array antenna is configured to perform 2-dimensional sensing on horizontal direction. However, in practical applications, the 2-dimensional sensing over only horizontal direction may receive reflections from objects (such as notice boards, traffic lights, bridges, buildings, etc.) which are higher than a horizontal plane. Due to hardware limitation, false alarm is usually caused and system performance is degraded. In such a situation, if the vehicle radar system provides an RF system with a three dimensional scanning function to sense over both horizontal direction and vertical direction simultaneously, reflections from horizontal direction and vertical direction are more distinguishable, such that system reliability is enhanced and false alarm rate is further reduced.
Traditionally, an intuitive way to obtain sensing capability on different directions is to deploy another set of array antennas, and arrange the array antennas so as to sense over vertical direction. However, vehicle radar systems utilize wireless signal transceivers disposed inside vehicle bumpers or grills for ranging and information exchange applications. Since shock-absorbing Styrofoam or glass fibers are usually disposed inside the vehicle bumpers, the available space is limited. It is hard to accommodate another set of array antennas. Furthermore, if the vehicle radar systems are produced for sales of after-market, i.e. vendors for the radar systems do not participate in decision-making of materials and thickness of the bumpers, in such a condition, design requirements for the array antenna gain, the area and the radiation patterns become stricter for adapting to different cars.
Therefore, how to adequately increase sensing directions or sensing range of the array antenna without substantially enlarging the disposal area of the array antenna is a significant objective in the field.